When I reviewed the OP-Z from Teenage Engineering, I was most curious about the expansion port. The diminutive portable synth and sequencer already packed a lot of musical power into a small box. The fact it could be further expanded was exciting. Today we're seeing one such example, with the announcement of the "rumble" module.
As the name suggests, the rumble module ($89) adds haptic feedback to the OP-Z, courtesy of a collaboration with Lofelt (of Basslet fame). At its most basic, rumble endows the OP-Z ($599) with a silent, vibrating metronome. Slot the module in, and you can feel the tempo, rather than hear it with the typical (and annoying) shrill "beep."